This forum is for other possible methods for fusion such as Sonolumenescense, Cold Fusion, CANR/LENR or accelerator fusion. It should contain all theory, discussions and even construction and URLs related to "other than fusor, fusion".
What ultimate pressure and operating pressure are you looking to achieve? What gas flow rates as well? Cryopumping definitely has the highest pumping speeds of any type of high vacuum pump, though it comes with its own unique costs and challenges. For this type of chamber, you are really limited to either diffusion or cryo, both of which require roughing before operating, though you are definitely getting to the size where cryo starts to make more sense. For any chamber though the pump has to be spec'd and sized properly for the system. If you have the infrastructure to support cryo, that can support both very clean and extremely fast pumping. I'd definitely be interested in hearing more about the pumping setup and chamber.